The present invention relates to pumping devices in which a flow of a small quantity of a first fluid through a passageway will induce a flow of a second fluid through the passageway. Such devices have particular application where a vessel containing a liquid has to be emptied, and more particularly where the second fluid is a liquid with entrained solids.
Pumps of the above type are used in the swimming pool industry to empty pool water filters where the filtering medium is sand. It is to be understood, however, that there are many other uses for such pumps. In the swimming pool industry sand filters are commonly used to treat the pool water and when the filtration efficiency falls the sand is removed and replaced. Pumps of the type to which this invention relates are commonly used for the sand removal because the construction makes it possible to enter the pump into the filtering material housing through a small access hole.
The pump of the type with which this invention is concerned includes, more particularly, a tubular body adapted at its discharge end for connection to a discharge hose with a bore mounted venturi type fitting adjacent its inlet end. There is a high pressure delivery pipe adapted at one end for coupling to a pressurised water supply, such as a garden tap. At the other end the delivery pipe has a small orifice discharge port aligned with the axis of the bore fitting and spaced from the inlet end of the tubular body. Whilst ever the inlet end of the tubular body is submerged in a liquid reserve a flow of high pressure water through the venturi type fitting will result in a negative pressure in the tubular body sufficient to draw liquid from the liquid reserve and discharge is through the outlet end of the tubular body.
The efficiency of the device is dependent on many factors including the pressure and volume of the supply liquid and the venturi provided enhancement of the negative pressure resulting from the high pressure flow of the supplied liquid.
In known pumps the venturi fitting is commonly made of a plastics material which will be eroded away in a relatively short time where water with entrained filtration sand is being pumped. It would therefore be desirable to provide an easily mounted and removed wear resistant venturi fitting.
Another problem with known pumps is their inability to handle water of shallow depth. This is because the high pressure water supply jet needs to be below and spaced from the inlet end of the tubular body thereby placing the inlet end of the tubular body as a substantial distance above the floor of the container being drained. it would be desirable to provide a pump which overcomes this problem.